Speed detecting devices for anti-lock braking systems for motor vehicles are not new per se, one such prior design is shown in U.S. Pat. No. 3,890,517. In the axle journals of the motor vehicle. The sensor bracket is mounted by two (2) screws to a bridge welded to the axle journal and has a through hole which is lined with a sleeve made of an elastomeric material. The rod shaped sensor is pressed into this sleeve by means of a special device.
The above design has certain disadvantages and drawbacks. For example, in spite of the relatively simple design of the known device, it is still necessary to have two (2) parts made of different materials. The elastomeric sleeve is a critical component by reason of the strict standards imposed on the sleeve as a result of the temperatures in dirty environmental conditions to which it is exposed. These conditions are especially critical with respect to the sleeve's resistance to aging. Further, because the intrinsic tension enforce of the sleeve alone is responsible for the reliable retention of the sensor, it has been found that the sensor can be displaced when the sleeve undergoes a small amount of fatigue. When this happens, the anti-lock braking system can fail.
In the known arrangement, the sensor is difficult to replace quickly and easily in the event that a defect is present. It has been found that either the sensor must be replaced completely together with the sensor bracket or the defective sensor must be removed and then a new sensor pressed into the sensor bracket by means of the special insertion tool. In both instances, the sensor bracket must first be detached from the mounting bridge.